Elongated catheters for obtaining access to a vascular system are well known in the art and have been used in the medical field for many years. Such catheters usually have an elongated body with proximal and distal ends. A catheter lumen is formed interiorly of the body. A hole or opening is located at the distal end of the elongated body so that fluid material can either pass from the catheter lumen through the hole into the vascular system or so that fluid from the vascular system may be drawn through the distal end hole into the catheter lumen to be withdrawn from the vascular system. Fluid material which is intended to be infused into the vascular system is introduced into the catheter lumen through its proximal end. Pressure responsive exits in the form of slits may be arranged in the side wall of the catheter body as a means for infusing fluid which is under a desired pressure from the catheter lumen into the vascular system at a desired rate and at a desired location.
Catheters of the foregoing type have been used for a variety of purposes. While some applications do not require that the catheter remain in the vascular system for any significant length of time, other uses or medical procedures, such as dialysis, may require that the catheter remain in the vascular system for long periods of time. While the typical catheter in use today is made of polymeric material, which is biocompatible, such materials are not of natural origin. As a result, the longer a catheter remains in the vascular system, the more likely it is that deposits of fibrin will form on the outside surface of the catheter body. Over time, such deposits will build up, forming a fibrin sheath along the outside surface of the catheter. The formation of fibrin build up and the creation of such a fibrin sheath on the outside surface of a catheter within a vascular system can have serious deleterious effects. Fibrin forms an attractive environment for the growth of bacteria. Although small amounts of bacteria in a human body may not cause serious problems as the natural defenses of the human body can combat the effects of such small amounts of bacteria, the presence of a fibrin build up or sheath provides an environment where bacteria can accumulate and grow. The growth of bacteria at such a site may therefore result in infections. The occurrence of such an infection will require a course of anti-biotic treatment and usually the removal of the catheter in order to overcome the bacterial infection and to allow the patient to recover from its effects. Not only will the patient now have to overcome the effects of an infection, but the patient is not receiving the benefit of the treatment which required the use of the catheter in the first place.
The build-up of a fibrin sheath on the outside wall of a catheter in a vascular system may also cause the partial or complete obstruction of holes and openings, such as at the distal end of the catheter, thereby ihibiting or preventing the passage of fluid material through the holes either into the vascular system or from the vascular system. Thus, when attempting to infuse or withdraw fluids into or from the vascular system, or during such procedures as dialysis, the catheter will not be able to handle the required flow rates.
Heretofore, the solution to the build up of a fibrin sheath has been to replace the catheter with a new one, requiring significant cost and time, or to physically remove the fibrin from the outside walls of the catheter body while the catheter remains in place within the patient's vascular system. The procedure to accomplish this removal of the fibrin sheath involves an additional entry into the patient's vascular system so that a mechanical device, such as an expanding basket or snare, may be inserted into the vascular system and manipulated to the site of the catheter. The basket or snare is then used to strip the fibrin build up from the outside surface of the catheter, thus freeing up the openings to allow fluid to pass through the catheter into or from the vascular system and to eliminate an environment that would promote the growth of bacteria. Such a procedure for stripping the fibrin material from the outside surface of the catheter, however, results in the sudden release and availability of large amounts of fibrotic material which may travel through the patient's vascular system to the lungs with disastrous results. In addition, the use of such mechanical devices as a basket or snare, will cause damage to the catheter which could result in its subsequent failure. Such a stripping procedure is also expensive.